The starting materials of the present invention, 3'-azidothymidine (which may also be named 3'-deoxyazidothymidine or AZT) 2',3'-dideoxyadenosine (ddA), 2',3'-dideoxyinsine (ddI), 2',3'-didehydrodideoxycytidine (d4C), 2',3'-didehydro-3'-deoxythymidine (d4T), 3'-fluoro-3'-deoxythymidine (FLT), 3'-azido-2',3'-dideoxyuridine (AZddU), carbocyclic-2',3'-didehydrodideoxyguanosine (Carbovir), 2'-deoxy-3'-thiacytidine (DTC) and the 2'-fluoro analogs of ddA, ddI and 2',3'-dideoxycytidine (ddC) are known nucleoside derivatives having anti-viral activity. With the discovery and proliferation of contagious, serious, sexually transmitted viral afflictions, anti-viral medicaments of increasing potency are actively sought.
One method of increasing potency is to increase dosage. However, the limitations of this method are quickly surpassed due to considerations restricting the feasible size of the dosage. More importantly, the toxicity of such anti-viral agents as AZT severely limits the maximum dosage that can be safely administered. Compounds with a favorable ratio of toxic does to effective dose, for example as measured by their cytotherapeutic index (ID.sub.50 /ED.sub.50), are required.